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An Urban Experience
purpose in dogs. The presence of autoagglutination
or severe hemolysis may preclude the crossmatch testing. A major crossmatch incompatibility is of greatest importance, because it predicts that the transfused donor cells will be attacked by the patient’s plasma, thereby causing a potentially life-threatening acute hemolytic transfusion reaction. Because fatal reactions may occur with less than 1 ml of incompatible blood, compatibility testing by administering a small amount
of blood is not appropriate; this has been shown
in experimental studies to potentially result in fatal reactions. A minor crossmatch incompatibility should not occur in dogs if canine donors have not been transfused previously and is of lesser concern because donor’s plasma volume is small, particularly with packed red cell products, and is diluted markedly in the patient. Do not use previously used dogs as donors.
The initial blood crossmatch between two dogs that
have never before received a transfusion should be compatible, because dogs do not have naturally occurring alloantibodies. Therefore, a crossmatch may be omitted before the first transfusion in clinical practice for dogs. Because the crossmatch does not determine the blood type of the patient and donor, a compatible crossmatch does not prevent sensitization of the patient against donor cells within 1 to 2 weeks. Thus, previously transfused dogs should always be crossmatched, even when receiving again blood from the same donor. The time span between the initial transfusion and incompatibility reactions may
be as short as 4 days and the induced alloantibody can last for many months to years (i.e., years after the last transfusion alloantibodies may be present). Again, a blood donor never should have received a blood transfusion to avoid sensitization. The practice of transfusing patients with the least compatible unit does not have any scientific basis. Nevertheless, some minor agglutination results in crossmatching a patient may be unrelated to alloantibodies and unspecific (e.g., patient’s RBC damage by uremia and other illnesses, donor cells after extended storage of unit in the refrigerator). Of course, any patient with true/persistent autoagglutination may not be matched to any donor.
Although transfusion of blood and its components is usually a safe and temporarily effective form of therapy, there is always a risk for potential hazards. Adverse reactions usually occur during or shortly after the transfusion and can be due to any component of whole blood. Most transfusion reactions can be avoided by carefully selecting only healthy donors; using appropriate collection, storage, and administration techniques; performing blood typing and crossmatching; and administering only the needed blood components.
Transfusion Reactions
While transfusion of blood and its components is usually a safe and temporarily effective form of therapy, there
is always a risk for potential hazards. Adverse reactions
usually occur during or shortly after the transfusion
and can be due to any component of whole blood. Most transfusion reactions can be avoided by carefully selecting only healthy donors, using appropriate collection, storage, and administration techniques, performing blood typing and crossmatching, and administering only needed blood components. The most common clinical sign of transfusion reaction is fever, followed by vomiting and hemolysis. Hemolytic transfusion reactions can be fatal and are, therefore, most important, while fever and vomiting are usually self-limiting. Adverse effects of transfusions can be divided into non-immunologic (pyrogen-mediated fever, transmission of infectious agents, vomiting, mechanical hemolysis, congestive heart failure, hypothermia, citrate toxicity, pulmonary complications) and immunologic reactions (acute and delayed hemolytic transfusion reactions, urticaria to anaphylaxis, acute respiratory distress, graft versus host disease). Note that some clinical signs may be caused by both mechanisms. Despite the variety of blood types and the limited degree of compatibility testing in clinical practice, transfusion reactions are rarely reported.
Blood Donors and Sources
Many larger veterinary hospitals have permanent canine and/or feline blood donors to cover their transfusion requirements or in case fresh whole blood or platelet-rich plasma (concentrate) is needed. Several larger voluntary blood donor programs have emerged with client or staff owned dogs. More than a dozen commercial canine
blood banks have been established in the United States and deliver overnight blood products. Autologous (self) transfusion refers to the donation of blood by a patient four weeks to a few days prior to surgery when major surgical blood loss is anticipated. Blood can also be collected immediately prior to surgery. The patient will be hemodiluted with crystalloid and colloid solution and receives the
blood when excessive bleeding occurs or after surgery. Autotransfusion is another autologous transfusion technique in which freshly shed blood salvaged intra-operatively or following trauma can be reinfused after careful filtering.
Blood donors should be young adult, lean, and good tempered animals, and weigh at least 23 kg for dogs (to donate 450ml); have no history of prior transfusion; have been regularly vaccinated and are healthy as determined by history, physical examination, and laboratory tests (complete blood cell count, chemistry screen, and fecal parasite examination every 6-12 months) as well as free of infectious diseases (testing depends on geographic area but may include regular microfilaria, Brucella, Hemomycoplasma, Babesia, Ehrlichia, Anaplasma, Borrelia, Leishmania spp. testing in dogs. Donors should receive a well-balanced, high performance diet, and may be supplemented twice weekly with ferrous sulfate (Feosal, 10 mg/kg), if bled frequently. Packed cell volume (PCV) or hemoglobin (Hb) should be
42ND WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND FECAVA 23RD EUROCONGRESS